As fuel economy standards are being increased on motor vehicles, a resulting higher focus is placed on improving fuel economy. Improved aerodynamics is a key to improving motor vehicle fuel economy, as is lowering the overall weight of the motor vehicle. At the same time, comfort in operating the motor vehicles is also high on consumer appeal and the overall quietness of motor vehicles is becoming more important to customers. Accordingly, reducing the amount of noise in the cabin of the motor vehicles is also important
To attempt to address these issues, manufacturers are adding more underbody covers and shields to close off sections of the underbody with large panels that serve the dual purpose of smoothing the underbody surface to improve aerodynamics of the motor vehicle by essentially enabling air to efficiently flow under the motor vehicle and closing off the underbody to reduce sound penetration in to the interior of the vehicle.
Most of the industry uses covers and shields made from very low cost polymers like polypropylene and high-density polyethylene (HDPE). To improve stiffness heat resistance and dimensional capabilities of the material fillers such as glass and talc are added. These blends are relatively cheap and are the traditional materials used in these applications. They however lack the properties of sufficient sound attenuation and heat deflection.
The melting point of HDPE is about 130° C. and the melting point of polypropylene is about 160° C. It is frequently required to place these parts under engines and near exhaust systems, where typically the heat generated by the engine and exhaust manifold require withstanding temperatures as high as 225° C. To correct for this serious shortcoming, manufacturers add a combination of heat shields and noise, vibration and harshness (NVH) pads (e.g. high-temperature needled polyester) to the back of these covering parts. However, adding the heat shields and pads significantly increases the overall weight of the vehicle. A material composition that can on its own withstand temperatures of at least 225° C. and suppress noise would remove any requirement for added heat shields and pads thereby providing a substantial benefit.